FIG. 8 is a schematic explanatory drawing showing an example of a conventional double-side polishing apparatus. As shown in FIG. 8, a double-side polishing apparatus 201 is an apparatus which enables rotation and revolution of a carrier 208 meshed between a sun gear 206 and an internal gear 207 by driving rotation of the sun gear 206 and rotates a lower turn table 202 and an upper turn table 203 in opposite directions to simultaneously polish both surfaces of a wafer W by polishing pads 204 attached to the upper and lower turn tables.
Further, a slurry supplying mechanism that supplies to a wafer W a slurry which increases a polishing efficiency for the wafer W and reduces heat generated in the upper and lower turn tables 202 and 203 is provided in the double-side polishing apparatus 201. This slurry supplying mechanism is a mechanism that supplies a slurry to slurry supply holes 205 provided in the upper turn table 203 from a slurry tank 209 through a slurry supply duct 210, powder rings 212, and slurry supply tubes 213 and allows the slurry to flow out from lower end openings of the slurry supply holes 205 toward the wafer W.
According to a conventional technology, both surfaces of a wafer are polished while uniformly supplying the same amount of slurry from each supply hole by using such a double-side polishing apparatus. Further, Japanese Patent Application Laid-open No. 2004-142040 or Japanese Patent Application Laid-open No. H11-262862 discloses a double-side polishing method using a double-side polishing apparatus having a different structure adopting, e.g., a compression transport scheme in relation to a slurry supply scheme.
However, in the conventional method or the double-sides polishing method disclosed above, when both surfaces of a wafer are polished, sag frequently occurs at an outer peripheral portion of the wafer after polishing, and a shape of a wafer surface is not flat, resulting in a problem of a quality.